Data from recent tryptophan incorporation studies indicate that a precursor molecule is involved in the biosynthesis of glucagon in islets of anglerfish, pigeon, guinea pig, and rat. The most compelling evidence for the existence of a glucagon precursor has come from the isolation and sequence analysis of an apparent fragment of proglucagon from commercially prepared bovine/porcine glucagon. Further investigation into the role of this precursor in glucagon biosynthesis is indicated. One of the objectives of the proposed research is the isolation and full structure determination of intact proglucagon and glucagon from anglerfish islet tissue. Additionally, since no information is available on the regulation of glucagon biosynthesis, we shall examine the effects of certain physiologic and pharmacologic agents on the synthetic process as an initial step in the elucidation of possible general regulatory mechanisms. Following tissue extraction, isolation of proglucagon and glucagon will be accomplished by gel filtration, ion exchange chromatography and other methods commonly used for protein purification. To determine the effects of various agents on glucagon biosynthesis, islets will be incubated in vitro in the presence of radioactively labeled tryptophan (an amino acid present in proglucagon but absent from anglerfish proinsulin and insulin) and the tested agent. Examination of rates of incorporation into proglucagon and conversion to glucagon will be compared with control values by scintillation counting of the eluates from tissue extract gel filtration and polyacrylamide gel electrophoresis. It is hoped that determination of the primary structure of proglucagon and elucidation of modes of biosynthetic control will provide an informational basis for further investigation of alpha cell hyposuppressibility which occurs in human diabetes.